Last Updated: 2003-07-21 16:27:52 -0400 (Reuters Health)

NEW YORK (Reuters Health) - Stroke is a very rare problem for children, but when it occurs, black children and boys appear to be at highest risk, new research indicates.

Stroke, a common problem for older people, is caused by a lack of blood flow to areas in the brain. This lack of flow is due to either blockage or damage of the blood vessels that feed the brain.

In adults, the risk of stroke depends on a person's race and gender, which can often be explained by factors such as smoking, diabetes, and high blood pressure.

"These explanations cannot be used to account for our findings" because "factors like [high blood pressure] and smoking do not play a significant role in childhood stroke," lead author Dr. Heather J. Fullerton, from the University of California at San Francisco, said in a statement.

"Additional...studies are needed to...shed light on why children have strokes," she added.

The new findings, published in the medical journal Neurology, are based on a study of children who were hospitalized with stroke in California during the 1990s.

During this period, 2278 children were admitted with strokes, the authors note. This amounts to an annual rate of about 2 cases per 100,000 children.

Black children were more than twice as likely as whites to suffer a stroke involving a blocked blood vessel and about 60 percent more likely to sustain a stroke involving blood vessel rupture. This held true even after eliminating cases related to sickle cell disease--a blood disorder that affects blacks much more often than whites.

Asians were just as likely as whites to sustain a stroke, while Hispanics were at lower risk for some types of stroke, the researchers found.

Boys were up to 34 percent more likely than girls to experience a stroke, the investigators note. This remained true even after eliminating cases related to trauma, a problem that usually involves boys rather than girls.

Gender, but not race, influenced whether the stroke was fatal. For example, 17 percent of boys who sustained a blockage-type stroke died, compared with only 12 percent of girls.